<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parent{
            width: 500px;
            height: 400px;
            border:1px solid red;
            margin:0 auto;
            display: flex;
            /* flex-direction: row;
            flex-wrap: wrap; */

            /* justify-content: flex-start;

            align-items:center; */

        }
        .child{
            /* width: 100px; */
            flex:1;
            height: 60px;
            color: white;

        }
        .second{
            flex:2;
        }
    </style>
</head>
<body>
<div class="parent">
    <div class="child" style="background-color:red ;">弹性元素1</div>
    <div class="child second" style="background-color:green ;">弹性元素2</div>
    <div class="child" style="background-color:orange ;">弹性元素3</div>
    <!-- <div class="child" style="background-color:black ;">弹性元素4</div>
    <div class="child" style="background-color: blue;">弹性元素5</div>
    <div class="child" style="background-color: yellow;">弹性元素6</div> -->
</div>
</body>
</html>